Bullet with chamber sealing structure and ammunition comprising same

ABSTRACT

A round of ammunition for use in a 5.56 NATO-specification chamber comprises a cartridge casing and a bullet having a casing engaging segment, a sealing band and a groove. The sealing band encircles the casing engaging segment. The casing engagement segment of the bullet is engaged within a bullet receiving opening of the cartridge casing with a rear surface of the sealing band abutting a front edge of the cartridge casing. The groove encircles the casing engagement segment. A rear portion of the sealing band intersects a front portion of the groove. A front face of the sealing band is substantially flat. An angle of the front face of the sealing band is approximately the same as an angle of a neck-to-throat transition portion of the 5.56 NATO-specification chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This continuation-in-part patent application claims priority from co-pending United States Non-provisional patent application having Ser. No. 13/066,780, filed Apr. 25, 2011, entitled “Subsonic Small-Caliber Ammunition And Bullet Used In Same”, having a common applicant herewith and being incorporated herein in its entirety by reference.

FIELD OF THE DISCLOSURE

The disclosures made herein relate generally to ammunition for firearms and, more particularly, to subsonic ammunition for use with semi and fully automatic weapons.

BACKGROUND

The projectile (i.e., bullet) from a fired weapon, particularly a rifle, typically leaves the muzzle of the weapon at a speed that is greater than the speed of sound, i.e. a muzzle velocity of greater than approximately 1086 ft/sec. at sea level under standard conditions of temperature and pressure. Such a speed is referred to as being supersonic. Causing the bullet to achieve supersonic speed is advantageous because the faster a projectile travels, the flatter is its trajectory to its intended target. Also, faster speeds of projectiles tend to reduce the effects of lateral wind forces upon the path of the projectile to its intended target.

Due to supersonic speed of a projectile enhancing its accuracy of delivery to an intended target, it can be seen why it is desirable for projectiles to have a supersonic muzzle velocity. However, projectiles travelling at supersonic speeds generate an audible sound during their free flight, which can undesirably be used to locate the source of the weapon from which the projectile was fired. Under certain circumstances of military operations and/or police operations, it is desirable that the source of the weapon firing a projectile not be identifiable by the sound generated by the travelling projectile. Furthermore, for a projectile of a given shape and mass, it is sometimes desirable for muzzle velocity to be used in limiting the potential for the projectile to strike a down-range object in the case with the projectile misses or passes through its intended target.

In certain situations, one approach for mitigating adverse concerns relating to supersonic muzzle velocity is to restrict the speed of travel of the projectile to a subsonic speed (i.e., a muzzle velocity of less than approximately 1086 ft/sec. at sea level under standard conditions of temperature and pressure). In doing so, the projectile does not generate an audible sound during its free flight, thus limiting the potential for locating the source of the projectile. Additionally, subsonic flight reduces the distance that a projectile can travel, thereby limiting the potential for the projectile to strike down-range objects.

In semi-automatic and fully automatic weapons, pressure (i.e., energy) generated by firing of a round of ammunition serves to energize the weapon's bolt actuation mechanism. As such, implementing subsonic flight of a projectile in a manner that reduces pressure within a weapon's barrel bore can result in there being insufficient energy generated during combustion of the ammunition to cycle the bolt in a semi-automatic or fully-automatic weapon and/or to lock the bolt in its open position upon the firing of the last round in the weapons' magazine. In some cases, gas pressure provided at a gas port of a weapon can be increased to suitable energizes a bolt-actuation mechanism of the weapon through use of a sound suppressor to sufficient levels. However, removal of the sound suppressor renders such weapon inoperable in its semi-automatic and/or automatic modes of operation when such pressure-deficient rounds of ammunition are used.

Accordingly, subsonic ammunition that is capable of providing sufficient energy for cycling the bolt actuation mechanism of a semi-automatic or fully automatic weapon without the use of a sound suppressor is advantageous, desirable and useful.

SUMMARY OF THE DISCLOSURE

Embodiments of the present invention are directed to bullets and rounds of ammunition that are configured for use with small-caliber semi-automatic and automatic weapons. More specifically, small-caliber bullets and rounds of ammunition configured in accordance with embodiments of the present invention provide subsonic flight when discharged in a semi-automatic or fully-automatic weapon and provide sufficient barrel bore pressure characteristics for cycling a gas-energized bolt actuation mechanism of such semi-automatic or fully-automatic weapon without the use of a sound suppressor to augment gas pressure within the barrel bore of the weapon. Ammunition configured in accordance with the present invention is well suited for applications where firepower is more of a consideration than is stealth. Accordingly, embodiments of the present invention advantageously overcome one or more shortcomings associated with some conventional small-caliber subsonic rounds of ammunition.

In one embodiment of the present invention, a bullet comprises a casing engaging segment defining a rear face of the bullet, a sealing band encircling the casing engaging segment, and a groove encircles the casing engagement segment at a position between the sealing band and the rear face of the bullet. A rear portion of the sealing band intersects a front portion of the groove.

In another embodiment of the present invention, a round of ammunition for use in a 5.56 NATO-specification chamber comprises a cartridge casing and a bullet having a casing engaging segment, a sealing band and a groove. The sealing band encircles the casing engaging segment. The casing engagement segment of the bullet is engaged within a bullet receiving opening of the cartridge casing with a rear surface of the sealing band abutting a front edge of the cartridge casing. The groove encircles the casing engagement segment. A rear portion of the sealing band intersects a front portion of the groove. A front face of the sealing band is substantially flat. An angle of the front face of the sealing band is approximately the same as an angle of a neck-to-throat transition portion of the 5.56 NATO-specification chamber.

In another embodiment of the present invention, a round of ammunition configured for use in a chamber of a firearm. Dimensions of a neck portion of the chamber and a throat portion of the chamber are configured in accordance with for the round of ammunition. The round of ammunition comprises a cartridge casing and a bullet having a casing engaging segment and a sealing band. The cartridge casing is configured in accordance with the specifications for the round of ammunition. The cartridge casing is configured with dimensions allowing the cartridge casing to be operably received within the neck portion of the chamber. The sealing band encircles the casing engaging segment. The bullet is engaged within a bullet receiving opening of the cartridge casing with a rear surface of the sealing band abutting a front edge of the cartridge casing. A maximum diameter of the sealing band is greater than a minimum diameter of the throat portion of the chamber.

These and other objects, embodiments, advantages and/or distinctions of the present invention will become readily apparent upon further review of the following specification, associated drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view showing a round of ammunition configured in accordance with a first embodiment of the present invention.

FIG. 1B is a fragmentary cross-sectional view of the round of ammunition of FIG. 1 showing orientation of elements thereof in relation to a mating chamber of a rifle barrel in which the round of ammunition is discharged.

FIG. 2 is a fragmentary cross-sectional view of the round of ammunition of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of a round of ammunition configured in accordance with a second embodiment of the present invention positioned within a mating chamber of a rifle barrel.

FIG. 4 is a side view showing a bullet of the round of ammunition shown in FIG. 3.

FIG. 5 is a fragmentary cross-sectional view of the rifle barrel shown in FIG. 3.

DETAILED DESCRIPTION OF THE DRAWING FIGURES

Referring to FIGS. 1A and 1B, a round of ammunition 100 configured in accordance with the present invention is shown. The round of ammunition 100 is configured for use with small-caliber semi-automatic and automatic weapons (e.g., a rifle). Advantageously, the round of ammunition 100 is configured to provide subsonic flight when discharged in a semi-automatic or fully-automatic weapon and to provide sufficient gas pressure characteristics for cycling a gas-energized bolt actuation mechanism of such semi-automatic or fully-automatic weapon without the use of a sound suppressor to augment gas pressure. In doing so, the round of ammunition 100 advantageously overcomes a key shortcoming associated with some conventional small-caliber subsonic rounds of ammunition.

The round of ammunition 100 includes a small-caliber cartridge casing 102 configured in accordance with specifications of a firearms standards organization for a weapon. The small-caliber cartridge casing 102 includes a first end portion 104 and a second end portion 106. Typically, a primer is mounted within the second end portion 106 thereby making the second end portion substantially closed. Preferably, but not necessarily, the small-caliber cartridge casing 102 can be made a metal material (e.g., brass) or from a polymeric material (e.g., nylon).

Standards for the shape and size of a cartridge for a certain weapons of a given caliber have been established and published by one or more various entities and/or organizations. Examples of such entities and/or organizations (i.e., firearm standards organizations) include, but are not limited to, Sporting Arms and Ammunition Manufacturers Institute (SAAMI), Permanent International Commission for Firearms Testing (CIP), and North Atlantic Treaty Organization (i.e., NATO). SAAMI, CIP, and NATO are examples of organisations that maintain standards that define respective specifications for firearms and components thereof (e.g., chamber specifications) and ammunition used therein. The NATO standard to defines NATO specifications for firearms and associated ammunition, the CIP standard to defines CIP specifications for firearms and associated ammunition, and the SAAMI standard defines SAAMI specifications for firearms and associated ammunition.

A rifle of the M4/M16/AR15 family of carbine rifles is a weapon that is capable of being operated in a semi-automatic mode and/or fully-automatic mode and that utilizes barrel bore pressure resulting from discharge of a round of ammunition to energize a bolt actuation mechanism of the weapon. Thus, in one embodiment, the round of ammunition 100 can be configured for use with a rifle of the M4/M16/AR15 family of carbine rifles. However, in view of the disclosures made herein, it is disclosed that a skilled person will appreciate other weapons for which a round of ammunition configured in accordance with the present invention will be useful and that embodiments of the present invention are not unnecessarily limited to use with any particular weapon (i.e., any particular rifle, piston, or other type of small-caliber firearm).

The round of ammunition 100 has a bullet 108 (i.e., a projectile) with a bearing surface portion 110 engaged within a bullet receiving opening 112 of the cartridge casing 102. The bullet receiving opening 112 is located at the first end portion 104 of the cartridge casing 102. Preferably, the bullet 108 is engaged within the bullet receiving opening 112 of the cartridge casing with a rear surface of the sealing band 121 abutting a front edge of the cartridge casing 102. In this manner, a propellant-receiving cavity 114 is formed within the cartridge casing 102 between its first and second end portions 104, 106. An ogive portion 116 (i.e., contoured tip portion) of the bullet 108 extends beyond the bullet receiving opening 112 and, optionally, some of the bearing surface portion can also extend beyond the bullet receiving opening 112.

As shown in FIGS. 1A, 1B, and 2, the bearing surface portion 110 of the bullet 108 has a sealing band 121 and sealing band receiving groove 123 therein. In one implementation (shown), the sealing band 121 is unitarily formed portion of the bullet 108. In an alternate implementation, the sealing band 121 is separately formed from a main body of the bullet 108 (i.e., portion comprising the bearing surface 110 and ogive portion 116) from a metallic or polymeric material and is subsequently attached to the main body of the bullet 108 by a suitable means (e.g., mechanical interlock, material-to-material bonding/welding, etc).

The sealing band 121 has an overall diameter that is greater than a diameter of the chamber throat portion 125 of a firearm chamber 127 and that is equal to or less than a diameter of a chamber neck portion 129 of the of a firearm chamber 127 (e.g., the minimum diameter of the chamber neck portion 129). Preferably, the volume of the sealing band receiving groove 123 is of a sufficient volume to receive therein all or a substantial portion of the material defining the sealing band 121 (e.g., the volume of the groove 123 is approximately equal to, equal to, or larger than a volume of the material defining the sealing band 121). For example, the sealing band receiving groove 123 can have a volume substantially the same as the volume of the sealing band 121. In this regard, when the bullet 108 is propelled past a chamber transition 131, the sealing band 121 is deformed (e.g., swagged) by contact with the chamber transition 131 and the sealing band receiving groove 123 serves as a space in which all or a portion of the material defining the sealing band 121 can become located (e.g., urged into the sealing band receiving groove 123 through contact with the chamber transition 131). The groove 123 preferably also has an arcuate cross-sectional profile (e.g., semi-circular, parabolic, concave, or the like) such that a surface of the groove 123 is devoid of edges.

A primary functionality of the sealing band 121 is to center and gas seal the bullet 108 when used in an over-sized throat such as the over-sized throat of the 5.56 NATO-specification chamber. The throat of the 5.56 NATO-specification chamber and chambers of firearms with a similar throat configurations are typically more than 0.002″ larger in diameter than conventional throats. These oversized throats allow gas to blow by the bullet in subsonic rounds and may lead to under pressure rounds. Accordingly, the sealing band 121 is designed to take up the space between the case mouth and the front of the chamber where the chamber neck uses typically a 45-degree angle to lead up to the chamber throat. In this regard, a maximum diameter of the sealing band 121 is preferably greater than a minimum diameter of the throat portion of the chamber such that the sealing band at least partially fills a space between the bullet 108 and a rifling groove bottom face of a barrel mated to the chamber. When a bullet configured in accordance with the present invention is intended for use in the 5.56 NATO-specification chamber (or suitably similarly configured chamber), there are preferred specifications for a sealing band in accordance with the present invention (e.g., the sealing band 121). One example of such preferred specifications are shown in Table 1 below.

Parameter Value Leading Edge Angle (A) Approximately the same as angle of chamber transition (e.g., about 45 degrees) transition (e.g., about 45 degrees) Effective Length (B) About 75% of horizontal distance (HD) between cartridge casing end face and chamber transition (e.g., about 0.010) Trailing Edge Angle (C) Approximately the same as angle of chamfer of cartridge casing mouth Height (D) Difference between radius of chamber at throat and radius of bullet at the bearing surface (e.g., preferably about 0.0019″ to about 0.0024″)

The effective length (B) of the sealing band 121 can be increased nominally if the mouth of the cartridge casing 102 is chamfered, which is commonly done to aid loading of bullets having a flat base. Alternately, the cartridge casing can be trimmed to a shorted length at the end face of its first end portion 104 from the maximum NATO-specification dimension in order to allow a width of the sealing band 121 to be increased.

The sealing band 121 can also serve to prevent the bullet 108 from being pushed back into the mouth of the cartridge casing 102 during loading into the firearm chamber 125. Because the sealing band 121 is larger in diameter than the inside diameter of the mouth of the cartridge casing 102, the sealing band 121 also functions to. Thus, the sealing band 121 eliminates the need to do any crimping (i.e., cannulating) of the cartridge casing 102, which his advantageous as crimping of a cartridge casing can and typically does causes damage to an engaged bullet. Still another function of the sealing band 121 is to provide a fluid resistant seal and the interface between the bullet 108 and the cartridge casing 102.

Another potential function of the sealing band 121 relates to providing a fluid-resistant seal between the bullet 108 and the cartridge casing 102. In one aspect of this functionality, if a trailing edge portion of the sealing band 121 and mating edge of the cartridge casing mouth are designed with mating profiled, (e.g., matched angles), the sealing band 121 can serve as an effective fluid-resistant sealing structure that can preclude the need for a ‘neck sealant’ that is often used in a mouth of a cartridge casing and/or or on the bearing surface portion of an associated bullet. Omission of the neck sealant is advantageous, as it is known to contaminate the barrel bore of a firearm from which ammunition having such neck sealant is fired. Furthermore, in cases where a neck sealant is used between the bullet 108 and the cartridge casing 102, swagging of the sealing band 121 into the sealing band receiving groove 123 will allow all or a significant portion of the neck sealant to be swagged into the sealing band receiving groove 123 and minimally contact the bore for a firearm from which the bullet 108 is fired. Furthermore, if a sealant is used only between the sealing band 121 and the mouth of the cartridge casing 102, the contact area and therefore the amount of neck sealant is going to be much less than in the conventional approach that coats the full inside of the cartridge case neck and corresponding length of the bullet with neck sealant.

A sealing band in accordance with the present invention can be formed using any suitable technique. In one sealing band forming technique, the sealing band is formed by placing a thin jacket bullet formed conventionally it in a die, which is split at the band location. The die is relieved with a ring that has the form of the band. Once the bullet is placed in the die, pressure is applied to cause the thin jacked to expand into this groove. In another sealing band forming technique, the sealing band is formed by electrochemical deposition of metal, guilding metal, copper, zinc. In still another sealing band forming technique, the sealing band is formed by injection of polymer (e.g., directly onto the bullet.

Turning now to a discussion of bullet constructions, in contrast to the monolithically formed bullet of FIGS. 1A, 1B, and 2, a bullet configured in accordance with an embodiment of the present invention can have a core made of a first type of metal disposed within a core-receiving cavity of a jacket made of a second type of metal. A jacket configured in accordance with the present invention can be made by the process of drawing metal (e.g., a sheet of metal) into a given shape and the bearing surface portion thereof can have a thickness of less than about 0.010″. In a preferred embodiment, the bearing surface portion has a nominal thickness between about 0.004″ and about 0.008″. Preferably, but not necessarily, the jacket is made from a copper alloy including about 90% copper (Cu) and up to about 10% zinc (Zn) and the core is made from a metal having lead as its major constituent component. In a preferred embodiment, the jacket is made from a copper alloy having a minimum of about 2% zinc.

It is disclosed herein that, in an alternate embodiment, the bullet 108 can have a core that is formed to provide the intended exterior profile of the bullet 108 and have a plated jacket provided over the core. In such an alternate embodiment, the core is formed to have precise dimensions and profile of the bullet 108 shown in FIGS. 1 and 2. The core is then plated using a suitable plating process to form the jacket to have a thickness that provides the bullet with required/intended finished dimensions. For example, the core can be plated to provide the bullet with an outside diameter at the bearing surface portion that is of a required/intended dimension.

As shown in FIG. 1A, the round of ammunition 100 has a propellant 124 (e.g., powder) within the propellant-receiving cavity 114. The propellant 124 can be a relatively slow burning type propellant that provides a rapid peak in pressure build up within the propellant-receiving cavity 114 and that maintains a broader burn duration than relatively fast burning type propellants. In one embodiment, the propellant 124 is configured by a manufacturer thereof for being used as a medium caliber ammunition propellant. One example of such a medium caliber propellant suitable for use with rounds of ammunition configured in accordance with the present invention has been offered from General Dynamics Corporation under propellant no. XPR 47C1. In view of the disclosures made herein, a skilled person will appreciate that other propellants of suitable specification can be used in rounds of ammunition configured in accordance with the present invention.

During firing of the round of ammunition 100 within a weapon, the propellant 124 in combination with the bullet 108 result in gas pressure characteristics and bullet-bore frictional characteristics that provide for subsonic flight of the bullet 108 and for sufficient gas pressure within a barrel bore of the weapon to cycling a gas-energized bolt actuation mechanism of the weapon. For a given configuration of ammunition (e.g., 5.56 mm NATO-specification ammunition), the bullet 108 will preferably be heavier (e.g., by as much as 12 grains) than a bullet with a standard thickness drawn-metal jacket (e.g., through use of a relatively thin jacket and greater volume of the core in the case of a jacketed projectile or through use of extra material in the ogive portion 116). When this relatively heavy, bullet is subjected to the heat and pressure of discharge of the propellant 108, the relatively weight of the bullet 108 will result in enhanced obturation of the bearing surface portion 110 of the bullet 108 within the barrel bore of the weapon such that sliding friction between the bearing surface portion 110 and barrel bore will be enhanced relative to a comparable bullet of conventional (i.e., prior art) construction.

In the case of a bullet configured in accordance with the present invention having a jacketed construction, sliding friction between the bore and the bullet will create heat in the jacket. The core (e.g., lead) has relatively low heat conductivity and the material of the jacket 120 (e.g., copper alloy) has relatively high heat conductivity. Heat produced within the jacket will penetrate the full thickness of the jacket within the time it takes for the bullet to pass down a length of the barrel bore of the weapon. When this heat reaches the core, the core serves as an effective insulator thereby causing more heat to building the jacket and, thus, soften the jacket further to provide for more sliding friction. Roughly speaking, given identical frictional heating, a jacket that is three times as thick as a thinner jacket will heat up about one-third of the amount that the thinner jacket will heat up. The friction coefficient of copper is a strong function of the surface hardness and hardness is a strong function of temperature. In this manner, the jacket being relatively thin further enhances sliding friction between the bearing surface portion and the barrel bore. In combination with these frictional and obturation considerations of such a jacketed bullet, the propellant 124 discussed above provides gas pressure characteristics (e.g., peak gas pressure, percent dwell around peak gas pressure, and average gas pressures) within the barrel bore of the weapon to generate sufficient gas-pressure derived energy at a gas port of the weapon for cycling its bolt carrier when a round of ammunition configured in accordance with the present invention is discharged. These gas pressure characteristics in combination with the increased weight of a bullet configured in accordance with an embodiment of the present invention and frictional forces exerted on the bullet will cause the bullet to decelerate from a supersonic speed (e.g., at a barrel position where the gas port is located) to a subsonic speed prior to exiting the barrel bore.

It is disclosed herein that the use of a layer of friction reducing material on the bearing surface portion 110 of the bullet 108 can be used to influence gas pressure characteristics and/or resulting velocity profile of the bullet 108. For example, as disclosed above, molybdenum disulfide is one example of a friction-reducing material composition to which the jacket 120 and the shot (e.g., steel shot) can be exposed during such shot peening for causing the exterior surface of the jacket 120 to become coated with a layer of molybdenum disulfide. Coating the bearing surface portion 110 with a layer of molybdenum disulfide or other suitable friction reducing material composition can result in the bullet exhibiting reduced initial friction in the barrel bore, with diminishing effect as velocity of the bullet 108 increases (e.g., provides negligible effect with suitable velocity). Thus, its application to the bearing surface portion 110 of the bullet 108 can result in lower initial gas pressure, which moderates and broadens the initial gas pressure spike produced by combustion of the propellant 120. In effect, such a layer of friction reducing material can delay onset of heating of the jacket and thus influence sliding friction as a function of time.

Referring now to FIGS. 3-5, various aspects of a round of ammunition 201 configured in accordance with a second embodiment of the present invention for use with a barrel 203 of a rifle (i.e., a firearm) are shown. It is disclosed herein that the round of ammunition can be constructed in a similar manner or the same manner as is described above with respect to the round to ammunition 100 discussed in reference to FIGS. 1A, 1B, and 2, particularly in regard to implementation of a sealing band configured in accordance with the present invention. In this regard, the sealing band 221 and groove 223 of the bullet 200 can be implemented and configured in a manner substantially or identically to the sealing band 121 and groove 123 of the bullet 108 discussed above in reference to FIGS. 1A, 1B, and 2.

The round of ammunition 201 has a bullet 200 (i.e., a projectile) engaged within a bullet receiving opening 205 of a small-caliber cartridge casing 207 thereby forming a propellant-receiving cavity 209 within the small-caliber cartridge casing 207. A propellant 211 is provided within the propellant-receiving cavity 209. The propellant 211 can be a relatively slow burning type propellant that provides a rapid peak in pressure build up within the propellant-receiving cavity 209 and that maintains a broader burn duration than relatively fast burning type propellants.

The bullet 200 includes a casing engaging segment 202, a rifling leade mating segment 204, and a tip segment 206. The rifling leade mating segment 204 has a frusto-conical shape tapering from a first diameter at its first end portion 208 to a second diameter at its second end portion 210. Frusto-conical refers to a cone whose tip has been truncated by a plane parallel to its base. The rifling leade mating segment 204 extends from a first end portion 212 of the casing engaging segment 202. The tip segment 206 extends from the second end portion 210 of the rifling leade mating segment 204. The first diameter is greater than the second diameter.

It is disclosed herein that the bullet 200 can be constructed and/or manufactured in the same or similar manner as the bullet 108. Accordingly, the bullet 200 can be constructed of a drawn jacket with a core therein, can be constructed of a preformed core having a plated jacket, or any other suitably configured construction.

Preferably, but not necessarily, the tip segment 206 includes a barrel bore engaging portion 214 extending from the second end portion 210 of the rifling leade mating segment 204. The barrel bore engaging portion 214 has a substantially cylindrical shape. A diameter of the barrel bore engaging portion 214 is substantially the same as the second diameter. The tip segment can also include a nose portion 215 having a substantially hemi-spherical shape. However, a bullet configured in accordance with the present invention is not limited to having a nose portion of any particular shape.

A bullet in accordance with the present invention can be configured as a 5.56 mm round of ammunition that is commonly used in a rifle such as an M4 carbine. Such a round of ammunition can be configured to have a second diameter that is about 0.2 inches. In the case of such round of ammunition having a bullet configured in accordance with the bullet 200 shown in FIGS. 4 and 5, the rifling leade mating segment of the bullet of that round of ammunition can have a conical taper CT, shown in FIG. 4, of about 2.4 degrees and a rifling leade mating segment having a length of about 0.2 inches. In an embodiment specific to a standard as provided by SAAMI, a rifling leade segment can have a conical taper of about 3.2 degrees. Accordingly, in view of the disclosures made herein, a skilled person will understand that the present invention is directed to substantially or approximately mating the rifling leade segment of a bullet to a rifling leade segment of a mating firearm's chamber and that the present invention is not unnecessarily limited to any particular conical taper of a rifling leade.

As shown in FIGS. 3 and 5, a rifling leade region 216 of the barrel 203 preferably has substantially the same profile and dimensions as the bullet 200. Advantageously, such a mating interface between the rifling leade mating segment 204 of the bullet 200 and the rifling leade region 216 of the barrel 203 limits a rate at which combustion gas can escape from a chamber 218 of the barrel 203 into its rifled bore 220. For cartridges with relatively low average and/or peak combustion gas pressure (e.g., subsonic cartridges), limiting the rate at which combustion gas can escape from a chamber 218 of the barrel 203 into its rifled bore 220 prior to the bullet 200 entering the rifled bore 220 increases a magnitude of combustion gas pressure in the chamber 218 and subsequently in the rifled bore 220 as the bullet 200 travels down the rifled bore 220. In this manner, a higher level of combustion gas pressure is available to a gas-energized cartridge cycling mechanism of the rifle for enabling operation in semi-automatic and fully-automatic modes of operation without a sound suppressor. In one such embodiment, a bullet/rifling leade interface precludes or substantially inhibits combustion gas from escaping from the chamber 218 of the barrel 203 into its rifled bore 220 prior to the bullet 200 entering the rifled bore 220. In contrast, in prior art implementations of bullet/rifling leade interfaces, the bullet has had a non-mating profile with respect to the rifling leade such that significant portions of combustion gas pressure is permitted to escape into the rifled bore of the barrel prior to the bullet entering the rifled bore of the barrel. As such, such prior art bullet/rifling leade interfaces have lead to unreliable if not unacceptable firearm performance in semi-automatic and fully-automatic modes of operation without a sound suppressor.

It is disclosed herein that configuring a round of ammunition in accordance with the present invention can include manipulating ammunition-specific parameters including, but not limited to, jacket thickness, jacket material composition, jacket hardness, bearing surface length, core material composition, propellant type, propellant quantity, and jacket surface coating presence/type. All or a portion of these ammunition-specific parameters can be manipulated in view of weapon-specific parameters including, but not limited to, barrel bore diameter, barrel bore length, gas port position/size, required bolt actuation mechanism energy, barrel bore material, etc. In view of the disclosures made herein, a skilled person will be able to specify ammunition-specific parameters for ammunition configured in accordance with the present invention for a particular configuration of weapon (e.g., a rifle) by experience and/or with minimal experimentation.

In the preceding detailed description, reference has been made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the present invention may be practiced. These embodiments, and certain variants thereof, have been described in sufficient detail to enable those skilled in the art to practice embodiments of the present invention. It is to be understood that other suitable embodiments may be utilized and that logical, mechanical, chemical and electrical changes may be made without departing from the spirit or scope of such inventive disclosures. To avoid unnecessary detail, the description omits certain information known to those skilled in the art. The preceding detailed description is, therefore, not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the appended claims. 

What is claimed is:
 1. A bullet, comprising: a casing engaging segment defining a rear face of the bullet; a sealing band encircling the casing engaging segment; and a groove encircles the casing engagement segment at a position between the sealing band and the rear face of the bullet, and wherein a rear portion of the sealing band intersects a front portion of the groove.
 2. The bullet of claim 1 wherein the groove has an arcuate cross-sectional profile such that a surface of the groove is devoid of edges.
 3. The bullet of claim 1 wherein: the rear portion of the sealing band includes a rear wall; the front portion of the groove includes a front wall; and the rear wall of the sealing band intersects the front wall of the groove.
 4. The bullet of claim 1 wherein a volume of the sealing band is approximately the same as a volume of the groove.
 5. The bullet of claim 4 wherein: the groove has an arcuate cross-sectional profile such that a surface of the groove is devoid of edges; the rear portion of the sealing band includes a rear wall; the front portion of the groove includes a front wall; and the rear wall of the sealing band intersects the front wall of the groove.
 6. The bullet of claim 1 wherein: the sealing band is substantially symmetric about a longitudinal centerline axis of the casing engaging segment; the groove is substantially symmetric about the longitudinal centerline axis of the casing engaging segment; and a volume of the sealing band is greater than or equal to the volume of the groove.
 7. The bullet of claim 1, further comprising: a rifling leade mating segment extending from the casing engaging segment forward of a front portion of the sealing band, wherein the rifling leade mating segment has a frusto-conical shape tapering from a first diameter at a first end portion thereof to a second diameter at a second end portion thereof and wherein the first diameter is greater than the second diameter; and an ogive portion extending from the second end portion of the rifling leade mating segment.
 8. The bullet of claim 7 wherein a volume of the sealing band is greater than or equal to the volume of the groove.
 9. The bullet of claim 8 wherein: the rear portion of the sealing band includes a rear wall; the front portion of the groove includes a front wall; and the rear wall of the sealing band intersects the front wall of the groove.
 10. The bullet of claim 9 wherein: the groove has an arcuate cross-sectional profile such that a surface of the groove is devoid of edges; and a volume of the sealing band is greater than or equal to the volume of the groove.
 11. A round of ammunition for use in a 5.56 NATO-specification chamber, comprising: a cartridge casing; and a bullet having a casing engaging segment, a sealing band and a groove, wherein the sealing band encircles the casing engaging segment, wherein the casing engagement segment of the bullet is engaged within a bullet receiving opening of the cartridge casing with a rear surface of the sealing band abutting a front edge of the cartridge casing, wherein the groove encircles the casing engagement segment, wherein a rear portion of the sealing band intersects a front portion of the groove, wherein a front face of the sealing band is substantially flat, and wherein an angle of the front face of the sealing band is approximately the same as an angle of a neck-to-throat transition portion of the 5.56 NATO-specification chamber.
 12. The round of ammunition of claim 11 wherein: the groove has an arcuate cross-sectional profile such that a surface of the groove is devoid of edges; the rear portion of the sealing band includes a rear wall; the front portion of the groove includes a front wall; and the rear wall of the sealing band intersects the front wall of the groove.
 13. The round of ammunition of claim 11 wherein a volume of the sealing band is greater than or equal to the volume of the groove.
 14. The round of ammunition of claim 11, further comprising: a rifling leade mating segment extending from the casing engaging segment forward of a front portion of the sealing band, wherein the rifling leade mating segment has a frusto-conical shape tapering from a first diameter at a first end portion thereof to a second diameter at a second end portion thereof and wherein the first diameter is greater than the second diameter; and an ogive portion extending from the second end portion of the rifling leade mating segment.
 15. A round of ammunition configured for use in a chamber of a firearm, wherein dimensions of a neck portion of the chamber and a throat portion of the chamber are configured in accordance with specifications of a firearms standards organization for the round of ammunition, the round of ammunition comprising: a cartridge casing configured in accordance with the specifications for the round of ammunition, wherein the cartridge casing is configured with dimensions allowing the cartridge casing to be operably received within the neck portion of the chamber; and a bullet having a casing engaging segment and a sealing band, wherein the sealing band encircles the casing engaging segment, wherein the bullet is engaged within a bullet receiving opening of the cartridge casing with a rear surface of the sealing band abutting a front edge of the cartridge casing, and wherein a maximum diameter of the sealing band is greater than a minimum diameter of the throat portion of the chamber.
 16. The round of ammunition of claim 15 wherein: a front face of the sealing band is substantially flat; and an angle of the front face of the sealing band is approximately the same as an angle of a neck-to-throat transition portion between the neck portion of the chamber and the throat portion of the chamber.
 17. The round of ammunition of claim 15, further comprising: a groove encircling the casing engagement segment; wherein a rear portion of the sealing band intersects a front portion of the groove; and wherein the groove has an arcuate cross-sectional profile such that a surface of the groove is devoid of edges.
 18. The round of ammunition of claim 17 wherein: the rear portion of the sealing band includes a rear wall; the front portion of the groove includes a front wall; and the rear wall of the sealing band intersects the front wall of the groove.
 19. The round of ammunition of claim 17 wherein a volume of the sealing band is greater than or equal to the volume of the groove.
 20. The round of ammunition of claim 15 further comprising: a groove encircling the casing engagement segment; a rifling leade mating segment extending from the casing engaging segment forward of a front portion of the sealing band, wherein the rifling leade mating segment has a frusto-conical shape tapering from a first diameter at a first end portion thereof to a second diameter at a second end portion thereof and wherein the first diameter is greater than the second diameter; and an ogive portion extending from the second end portion of the rifling leade mating segment; wherein a rear portion of the sealing band intersects a front portion of the groove; wherein a front face of the sealing band is substantially flat; wherein the rear portion of the sealing band includes a rear wall; wherein the front portion of the groove includes a front wall; wherein the rear wall of the sealing band intersects the front wall of the groove; and wherein an angle of the front face of the sealing band is approximately the same as an angle of a neck-to-throat transition portion between the neck portion of the chamber and the throat portion of the chamber. 